Refining process

ABSTRACT

An iron refining process in a convertor in which oxidizing gas is blown laterally into a molten metal by means of two horizontal tuyeres and whose axes are inclined in opposite directions in respect to the diametral plane of the convertor equidistant between the points at which the axes of the two tuyeres pass through the internal surface of the convertor, and the apparatus for carrying out the process.

United States Patent 1191 Etienne 5] Dec. 16, 1975 REFINING PROCESS 3.706.549 12/1972 Knuppel 75/60 [75] lnventor: Arlette Therese Etienne, Boncelles,

Belglum Primary Examiner-Jeter D. Rosenberg [73] Assignee: Centre de Recherches Attorney, Agent, or FirmLawrence I. Field Metallurgiques, Liege, Belgium [22] Filed: July 2, 1974 21 Appl. No.: 485,198 ABSTRACT 30 F A D An iron refining process in a convertor in which oxiorelgn pplcauon lomy ata dizing gas is blown laterally into a molten metal by July 10, 1973 Belgium 802163 m ans of two horizontal tuyeres and whose axes are inclined in opposite directions in respect to the diame- [52] US. Cl.2 75/60 plane f th o rter equidistant between the [51] Int. Cl. C21C 5/34 points at which the axes of the two tuyeres pass [58] Field of Search 75/53, 60, 59 th gh the i ternal urface of the converter, and the apparatus for carrying out the process. [56] References Cited UNITED STATES PATENTS 6 Claims 2 Drawing Figures 3,015,554 l/l962 Rummel 75/60 1 i; z; a I 4 I l f j I l IO US. Patent Dec. 16, 1975 REFININGPROCESS The present invention relates to an iron refining converter having tuyeres for blowing oxidising gas into the hot metal below its upper surface.

A method of refining pig iron has been developed in recent years in which the refining gas, in this case pure oxygen, is injected through tuyeres into a converter either at the bottom or laterally underthe upper surface of the molten metal inside the converter. To avoid rapid wear of the refractory parts of the bottom or the walls, the tuyeres through which the refining gas is injected each consist of two coaxial tubes, the central tube being used for injecting the oxygen and the peripheral tube being used for injecting a suitable protective fluid. i

In order to reduce the duration of the refining operation as far as possible, specialists have attempted to increase the supply of refining oxygen so that the greatest possible amount of metal in the bath is subject to refining reactions in the shortest possible time.

It is therefore easy to appreciate that the number and position of the tuyeres used for injecting the refining gas can have a great influence on the speed and efficiency of the reactions, starting with the conversion process.

Specialists have also been confronted with other problems, e.g. metal being projected out of the converter caused for example by the bath oscillating, the metal boiling, or jets of oxygen striking the bath, and the problem of wear of the refractory parts mainly due to the rotation of the bath or possible impact of the jet or jets of oxygen against the wall.

A certain number of lateral tuyere arrangements have already been put forward in an effort to reduce unwanted movements of the bath (for example oscillations) without reducing the speed of the physicochemical reactions and without causing abnormal wear of the refractory lining by rotation of the bath. The solutions proposed have not been entirely satisfactory from either aspect.

What is desired is an arrangement of tuyeres which reduces to a great considerable extent untimely movements of the bath as well as the concomitant wear of the refractory parts, and reduces projections, while maintaining a high refining rate. The tuyeres used are preferably of the two coaxial conduit type, the central conduit being used for injecting oxidizing gas and the peripheral conduit for injecting a suitable protective fluid.

The invention will be further understood from the description which follows, taken with the drawings in which:

FIG. 1 is a vertical section through the convertor of FIG. 2 taken in the plane of a tuyere; and FIG. 2 is a plan view in section through the convertor of Figure taken in plane IIII of FIG. 1.

Before describing the invention in detail the expressions zero point and base plane relating to a tuyere will first be defined: the zero point is the point at which the axis of the tuyere passes through the internal surface of the converter wall; the base plane is the plane perpendicular to the converter axis and containing the zero point.

As shown in the drawings present invention provides an iron refining process in which iron is refined in a converter by lateral injection of an oxidizing gas under the level of the molten metal 12, and in which, assuming that the converter is vertical, the gas is injected through two tuyeres 14 which are horizontal or approximately horizontal and whose axes 18 are inclined in opposite directions in respect of the diametral plane 18 of the converter equidistant between the zero points 20 of the two tuyeres, the axes 16 of the two tuyeres or their projections in their respective base planes each forming an angle 22 of not less than 5 and not more than 20 with the line joining the centre 24 of the base plane II'II of the tuyere to its zero point, any point of intersection of the two axes or of their projection in the'same base plane being on the other side of the converter axis with respect to the straight line joining the two zero points of the'tuyeres, the zero points being separated in respect of the horizontal by an are 26 of 40 to 135, preferably and (this can be a great advantage because it means that thetuyeres can be arranged at a distance from the trunnions so as to be readily accessible for repair or maintenance).

Accordingly, the invention provides an iron refining converter having two tuyeres for blowing oxidising gas into the hot metal below its upper surface, in which, assuming the axis of the converter to be vertical, the two tuyeres have substantially horizontal axes inclined in opposite directions with respect to the diametral plane of the converter which is equidistant from the respective zero points (as defined hereinbefore) of the tuyeres, the projection of the axis of each tuyere in a horizontal plane forming an angle of 5 to 20 with the diameter passing through its zero point, the intersection, if any, of the projections of the tuyere axes in a common horizontal plane being remote from the straight line joining the zero points "with respect to the converter axis 30, the projection of the zero points in a common horizontal plane being separated by an arc whose angle is 40 to In another advantageous embodiment of the converter, the two tuyeres are positioned between two set levels, the upper level being at the middle of the depth of the metal bath, counted from the lowest level of the interior surface of the converter bottom, which is considered as new, the lower level being at least 20 cm above the said lowest level, the depth of the bath being considered as that which corresponds to the nominal capacity of the converter, assuming this is to be in a vertical position. This embodiment ensures a long period of stable operation for the converter, taking into account wear of the bottom and converter wall lining.

If the two tuyeres are arranged at the same level in the converter, this further decreases the risk of substances being projected out of the converter.

One particularly important way of applying the method is to blast the gas through the two tuyeres at differing pressures so that one tuyere will inject a larger amount of oxidizing gas than the other, thus causing the metal to rotate; this in turn helps to increase the metalslag interface area and intensifies mixing of the metal. By carefully varying the difference between the pres sures in the two tuyeres, an operator can easily control the rotation of the bath, speed it up, slow it down, or even stop it abruptly or rotate it in the opposite direction, according to operational requirements and degree of mixing desired.

What we claim is:

1. An iron refining process carried out in an iron refining converter having two tuyeres for blowing oxidising gas into the hot metal below its upper surface, in

3 which, assuming the axis of the converter to be vertical, the two tuyeres have substantially horizontal axes inclined in opposite directions with respect to the diametral plane of the converter which is equidistant from the respective zero points (as defined hereinbefore) of the tuyeres, the projection of the axis of each tuyere in a horizontal plane forming an angle of 5 to 20 with the diameter passing through its zero point, the intersection, if any, of the projections of the tuyere axes in a common horizontal plane being remote from the straight line joining the zero points with respect to the converter axis, the projection of the zero points in a common horizontal plane being separated by an arc whose angle is 40 to 135, wherein oxidizing gas is blown into the molten iron to be refined through the two tuyeres simultaneously.

2.'A process as claimed in claim 1, in which the angle of the said are is 70 to 100.

3. A process as claimed in claim 1, in which the zero points of the tuyeres lie between two given levels, the upper level being the middle of the depth of the bath, of hot metal, reckoned from the lowest level of the internal surface of the converter bottom, the lower level being at least 20 cm above the said lowest level, the converter bottom being considered as new, the depth of the bath being considered as that which corresponds to the nominal capacity of the converter.

4. A process as claimed in claim 1, in which the zero points of the tuyeres lie in the same horizontal plane.

5. A process as claimed in claim 1 in which each tuyere has two conduits, one within the other.

6. A process as claimed in claim 1, in which the gas pressure in one tuyere is different from that in the other, thus causing the bath to rotate, the rotational movement being controlled by varying the pressures in the tuyeres. 

1. AN IRON REFINING PROCESS CARRIED OUT IN AN IRON REFINING CONVERTED HAVING TWO TUYERES FOR BLOWING OXIDISING GAS INTO THE HOT METAL BELOW ITS UPPER SURFACE, IN WHICH ASSUMING THE AXIS OF THE CONVERTER TO BE VERTICAL, THE TWO TUYERES HAVE SUBSTANTIAL TIALLY HORIZONTAL AXES INCLINDED IN OPPOSITE DIRECTIONS WITH RESPECT TO THE DIAMETRAL PLANE OF THE CONVERTER WHICH IS EQUIDISTANT FROM THE RESPECTIVE ZERO POINTS (AS DEFINED HEREINBEFORE) OF THE TUYERES, THE PROJECTION OF THE AXIS OF EACH TUYERE IN A HORIZONTAL PLANE FORMING AN ANGLE OF 5* TO 20* WITH THE DIAMETER PASSING THROUGH ITS ZERO POINT, THE INTERSECTION, IF ANY, OF THE PROJECTIONS OF THE TUYERE AXES IN A COMMON HORIZONTAL PLANE BEING REMOTE FROM THE STRAIGHT LINE JOINING THE ZERO POINTS WITH RESPECT TO THE CONVERTER AXIS, THE PROJECTION OF THE
 2. A process as claimed in claim 1, in which the angle of the said arc is 70* to 100*.
 3. A process as claimed in claim 1, in which the zero points of the tuyeres lie between two given levels, the upper level being the middle of the depth of the bath, of hot metal, reckoned from the lowest level of the internal surface of the converter bottom, the lower level being at least 20 cm above the said lowest level, the converter bottom being considered as new, the depth of the bath being considered as that which corresponds to the nominal capacity of the converter.
 4. A process as claimed in claim 1, in which the zero points of the tuyeres lie in the same horizontal plane.
 5. A process as claimed in claim 1 in which each tuyere has two conduits, one within the other.
 6. A process as claimed in claim 1, in which the gas pressure in one tuyere is different from that in the other, thus causing the bath to rotate, the rotational movement being controlled by varying the pressures in the tuyeres. 